mfd: cros_ec: spi: Add mutex to cros_ec_spi

The main transfer function for cros_ec_spi can be called by more than
one client at a time.  Make sure that those clients don't stomp on
each other by locking the bus for the duration of the transfer
function.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Andrew Bresticker <abrestic@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index c185eb67943f..a2a605de79a7 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -65,11 +65,13 @@
  *      if no record
  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  *      is sent when we want to turn off CS at the end of a transaction.
+ * @lock: mutex to ensure only one user of cros_ec_command_spi_xfer at a time
  */
 struct cros_ec_spi {
         struct spi_device *spi;
         s64 last_transfer_ns;
         unsigned int end_of_msg_delay;
+        struct mutex lock;
 };
 
 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
@@ -208,6 +210,13 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
         int ret = 0, final_ret;
         struct timespec ts;
 
+        /*
+         * We have the shared ec_dev buffer plus we do lots of separate spi_sync
+         * calls, so we need to make sure only one person is using this at a
+         * time.
+         */
+        mutex_lock(&ec_spi->lock);
+
         len = cros_ec_prepare_tx(ec_dev, ec_msg);
         dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 
@@ -260,7 +269,7 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
                 ret = final_ret;
         if (ret < 0) {
                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
-                return ret;
+                goto exit;
         }
 
         /* check response error code */
@@ -269,14 +278,16 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
                 dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n",
                          ec_msg->cmd, ptr[0]);
                 debug_packet(ec_dev->dev, "in_err", ptr, len);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto exit;
         }
         len = ptr[1];
         sum = ptr[0] + ptr[1];
         if (len > ec_msg->in_len) {
                 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
                         len, ec_msg->in_len);
-                return -ENOSPC;
+                ret = -ENOSPC;
+                goto exit;
         }
 
         /* copy response packet payload and compute checksum */
@@ -293,10 +304,14 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
                 dev_err(ec_dev->dev,
                         "bad packet checksum, expected %02x, got %02x\n",
                         sum, ptr[len + 2]);
-                return -EBADMSG;
+                ret = -EBADMSG;
+                goto exit;
         }
 
-        return 0;
+        ret = 0;
+exit:
+        mutex_unlock(&ec_spi->lock);
+        return ret;
 }
 
 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
@@ -327,6 +342,7 @@ static int cros_ec_spi_probe(struct spi_device *spi)
         if (ec_spi == NULL)
                 return -ENOMEM;
         ec_spi->spi = spi;
+        mutex_init(&ec_spi->lock);
         ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
         if (!ec_dev)
                 return -ENOMEM;